[Spoilers for V13]
For what I have seen it looks like the bad ending happens in a certain moment in chapter 15. I was checking tvtropes to see if any info was added after the new version came out and it looks like it did (btw huge props to the one that added the info, that was really fast). There are many new bits of info there but the one that got the most of my attention was one in the "Characters" section, under the protagonist part to be exact. It talks about the "bad options" the character can take and, I suppose with enough points, you can betray your friends like it says here:
I would really like seeing someone get this part in their let's play, but let's be honest, it's really difficult to "screw up" that much not intentionally. The same thing happened with Florin's excecution, I was only able to find about it again due to tvtropes, but no playthrough had the scene because of the specific circumstances that it needed to happen.